U.S. patent number 5,296,874 [Application Number 07/778,280] was granted by the patent office on 1994-03-22 for thermal printer.
This patent grant is currently assigned to Fuji Photo Film Co., Ltd.. Invention is credited to Atsushi Nagata, Masaaki Orimoto, Yoshiyuki Watanabe.
United States Patent |
5,296,874 |
Nagata , et al. |
March 22, 1994 |
Thermal printer
Abstract
A thermal printer in which a sheet of recording paper is held by
and between a thermal print head includes a plurality of heat
generating elements and a platen drum, the amounts of heat of the
heat generating elements are selectively changed, and an image is
printed onto the recording paper. In the thermal printer, a
printing position is set just behind a clamp position at which a
clamp clamps the leading end of the recording paper onto the platen
drum. Therefore, the image printing can be started immediately
after the clamp position passes through the thermal head, with the
recording paper being in part wound around the platen drum by the
thermal printer. As a result, the time taken from paper feeding to
printing starting can be reduced.
Inventors: |
Nagata; Atsushi (Tokyo,
JP), Orimoto; Masaaki (Tokyo, JP),
Watanabe; Yoshiyuki (Tokyo, JP) |
Assignee: |
Fuji Photo Film Co., Ltd.
(Kanagawa, JP)
|
Family
ID: |
27580491 |
Appl.
No.: |
07/778,280 |
Filed: |
October 17, 1991 |
Foreign Application Priority Data
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Oct 19, 1990 [JP] |
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2-282753 |
Oct 19, 1990 [JP] |
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2-282754 |
Oct 20, 1990 [JP] |
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2-282660 |
Oct 20, 1990 [JP] |
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2-282661 |
Oct 20, 1990 [JP] |
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2-282662 |
Oct 20, 1990 [JP] |
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2-282663 |
Oct 20, 1990 [JP] |
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2-282664 |
Oct 20, 1990 [JP] |
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2-282666 |
Oct 20, 1990 [JP] |
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2-282667 |
Oct 20, 1990 [JP] |
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2-282668 |
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Current U.S.
Class: |
347/218; 101/409;
346/138; 347/214; 400/120.04; 400/624; 400/629; 400/642; 400/643;
400/644; 400/645 |
Current CPC
Class: |
B41J
2/325 (20130101) |
Current International
Class: |
B41J
2/325 (20060101); B41J 002/325 () |
Field of
Search: |
;346/76PH,138
;400/120,642,643,644,645,624,629 ;271/277 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Fuller; Benjamin R.
Assistant Examiner: Tran; Huan
Claims
We claim:
1. A thermal printer comprising:
a recording paper storage part for storing a plurality of sheets of
recording paper respectively cut to a given length and piled on one
another;
recording paper feed-out means for feeding out said recording paper
sheet by sheet from said recording paper storage part;
a platen drum for winding said recording paper fed out by said
recording paper feed-out means around a peripheral surface of said
platen drum;
clamp means for clamping a leading end of said recording paper to
said platen drum;
a thermal print head having a printing position being set just
behind a clamp starting position of said clamp means for printing
an image onto said recording paper disposed on said platen drum
while said platen drum is rotating; and
a paper discharge tray part for receiving said recording paper
conveyed through a discharge passage way which has the entrance of
said discharge passage way located just near the down stream of
said thermal print head by said platen drum when said platen drum
is rotated after completion of printing said image onto said
recording paper.
2. A thermal printer as set forth in claim 1, further comprising
oscillatory arm located at a paper feed position, wherein said
recording paper feed-out means includes a paper feed roller
supported at a tip end of said oscillatory arm means, and wherein
said paper feed roller is in contact with said recording paper in a
paper feed mode in a feed-out opening formed in said recording
paper storage part and also at a paper non-feed position and said
paper feed roller is kept away from said recording paper storage
part in a paper non-feed mode, and said oscillatory arm means can
be secured by a securing member at said paper non-feed position in
said paper non-feed mode.
3. A thermal printer as set forth in claim 1, wherein said thermal
print head includes hold portions located at first and second sides
thereof and said thermal print head is slightly movably supported
at the hold portions in a recording paper conveying direction and
in a direction perpendicular to said recording paper conveying
direction and also said thermal print head is positioned in such a
manner that said thermal print head can be moved in an axial
direction of said platen drum, said thermal print head being
energized in one side by a spring member.
4. A thermal printer as set forth in claim 1, further comprising
sensor means including a light emitting part for emitting light
toward said platen drum, reflecting means disposed on said platen
drum for reflecting said light from said light emitting part, a
light receiving part for receiving said light reflected by said
reflecting means outside said platen drum, and wherein said light
emitting part, said reflecting means and said light receiving part
respectively are located at a position where said light from said
light emitting part can be shielded by said recording paper at a
clamp position of said recording paper on said platen drum and are
also located at a position where a home position of said platen
drum can be detected before said recording paper arrives at said
clamp position on said platen drum.
5. A thermal printer as set forth in claim 1, comprising:
an ink sheet cassette including an ink sheet supply shaft and an
ink sheet take-up shaft;
an ink sheet supply reel engageable with said ink sheet supply
shaft;
an ink sheet take-up reel engageable with said ink sheet take-up
shaft; and
a reversal preventive mechanism disposed on said ink sheet take-up
reel.
6. A thermal printer comprising:
a recording storage part for storing a plurality of sheets of
recording paper respectively cut to a given length and piled on one
another;
recording paper feed-out means for feeding out said recording paper
sheet by sheet from said recording paper storage part;
a platen drum for holding a leading end of said recording paper fed
out by said recording paper feed-out means and winding said
recording paper around a peripheral surface of said platen
drum;
a thermal print head for printing an image onto said recording
paper disposed on said platen drum while said platen drum is
rotating;
a paper discharge tray part for receiving said recording paper
conveyed thereto by said platen drum when said platen drum is
rotated after completion of printing of said image; and
rotary paper guide means constructed so as to be rotatable around
said platen drum for guiding a trailing end of said recording paper
to a paper discharge passage at the completion of printing of said
image.
7. A thermal printer as set forth in claim 6, further comprising
movable paper guide means linked with said recording paper feed-out
means for moving by operating of said recording paper feed-out
means, an end portion of said movable paper guide means is
retreated from an ink sheet cassette during printing, and when said
recording paper is discharged after completion of printing of said
image, the end portion of said movable paper guide means is
inserted into said ink sheet cassette to thereby prevent the
trailing end of said recording paper from entering said ink sheet
cassette.
8. A thermal printer comprising:
a recording paper storage part for storing a plurality of sheets of
recording paper respectively cut to a given length and piled on one
another;
recording paper feed-out means for feeding out said recording paper
sheet by sheet from said recording paper storage part;
a platen drum for holding a leading end of said recording paper fed
out by said recording paper feed-out means and winding said
recording paper around a peripheral surface of said platen
drum;
a thermal print head for printing an image onto said recording
paper on said platen drum while said platen drum is rotating;
a paper discharge tray part for receiving said recording paper
conveyed thereto by said platen drum when said platen drum is
rotated after completion of printing of said image; and
a paper feed and discharge passage having an opening formed in a
paper guide around said platen drum with an oscillatory piece
member which is free to oscillate, for closing said opening, and
when said recording paper is conveyed by said platen drum, said
oscillatory piece member closes said opening in said paper feed and
discharge passage to thereby guide said recording paper.
9. A thermal printer comprising:
a recording paper storage part for storing a plurality of sheets of
recording paper respectively cut to a given length and piled on one
another;
recording paper feed-out means for feeding out said recording paper
sheet by sheet from said recording paper storage part;
a platen drum for winding said recording paper fed out by said
recording paper feed-out means around a peripheral surface of said
platen drum;
a thermal print head for printing an image onto said recording
paper on said platen drum while said platen drum is rotating;
a paper discharge tray part for receiving said recording paper
conveyed thereto by said platen drum when said platen drum is
rotated after completion of printing of said image; and
a plurality of paper guides, which are disposed around said platen
drum and spaced at a given distance from said platen drum, having
connecting portions and each of said plurality of paper guides are
connected to one another by a respective one of said connecting
portions and a forward end of at least one set of said connecting
portions in a direction in which said recording paper is conveyed
by said platen drum is positioned nearer to said platen drum than a
trailing end thereof in the direction in which said recording paper
is conveyed by said platen drum.
10. A method for printing an image by a thermal printer, comprising
the steps of:
(a) storing a plurality of sheets of recording paper in a recording
paper storage part which have been cut to a given length and piled
on one another;
(b) feeding out said recording paper sheet by sheet from said
recording paper storage part;
(c) winding said recording paper fed out at said step (b) around a
peripheral surface of a platen drum;
(d) clamping a leading end of said recording paper to said platen
drum by clamp means;
(e) setting a thermal print head just behind a clamp starting
position of said clamp means;
(f) printing the image onto said recording paper disposed on said
platen drum while said platen drum is rotating by said thermal
print head; and
(g) receiving said recording paper in a paper discharge tray
through a discharge passage way which has the entrance of said
discharge passage way located just near the down stream side of
said thermal print head by rotating said platen drum after
completion of said step (f).
11. A method as set forth in claim 10, further comprising the step
of (h) detecting a home position of said platen drum before said
recording paper arrives at a clamp position of said recording paper
on said platen drum, said step (h) including the steps of,
emitting light toward said platen drum by a light emitting
part,
receiving said light reflected by said reflecting means outside
said platen drum by a light receiving part,
said light emitting part, said reflecting means and said light
receiving part being respectively located at a position where said
light from said light emitting part can be shielded by said
recording paper at said clamp position.
12. A method for printing an image by a thermal printer, comprising
the steps of:
(a) storing a plurality of sheets of recording paper in a recording
paper storage part which have been cut to a given length and piled
on one another;
(b) feeding out said recording paper sheet by sheet from said
recording storage part by recording paper feed-out means;
(c) holding a leading end of said recording paper fed out at said
step (b) onto a platen drum;
(d) winding said recording paper around a peripheral surface of
said platen drum;
(e) printing the image onto said recording paper disposed on said
platen drum by a thermal print head while said platen drum is
rotating;
(f) receiving said recording paper in a paper discharge tray by
rotating said platen drum after completion of said step (e);
and
(g) guiding a trailing end of said recording paper to a paper
discharge passage by rotary paper guide means, which rotate around
said platen drum, at the completion of said step (e).
13. A method as set forth in claim 12, further comprising the steps
of:
(h) moving movable paper guide means linked with said recording
paper feed-out means in response to the operation of said recording
paper feed-out means;
(i) retreating an end portion of said movable paper guide means
from an ink sheet cassette during printing of said image; and
(j) inserting the end portion of said movable paper guide means
into said ink sheet cassette when said recording paper is
discharged after completion of printing of said image so that the
trailing end of said recording paper is prevented from entering
said ink sheet cassette.
14. A method for printing an image by a thermal printer, comprising
the steps of:
(a) storing a plurality of sheets of recording paper in a recording
paper storage part which have been cut to a given length and piled
on one another;
(b) feeding out said recording paper sheet by sheet from said
recording paper storage part;
(c) holding a leading end of said recording paper fed out at said
step (b) onto a platen drum;
(d) winding said recording paper around a peripheral surface of
said platen drum;
(e) printing the image onto said recording paper on said platen
drum while said platen drum is rotating;
(f) receiving said recording paper in a paper discharge tray by
rotating said platen drum after completion of said step (e);
and
(g) closing an opening in a paper feed and discharge passing formed
in a paper guide around said platen drum with an oscillatory piece
member, which is free to oscillate, and when said opening in said
paper feed and discharge passage by said oscillatory piece member
to guide said recording paper.
15. A method for printing an image by a thermal printer, comprising
the steps of:
(a) storing a plurality of sheets of recording paper in a recording
paper storage part which have been cut to a given length and piled
on one another;
(b) feeding out said recording paper sheet by sheet from said
recording paper storage part;
(c) winding said recording paper fed out at said step (b) around a
peripheral surface of a platen drum;
(d) printing the image onto said recording paper on said platen
drum while said platen drum is rotating;
(e) receiving said recording paper in a paper discharge tray by
rotating said platen drum after completion of said step (d);
and
(f) connecting a plurality of paper guides, which are disposed
around said platen drum and spaced at a given distance from said
platen drum, having connecting portions for connecting each of said
plurality of paper guides to one another by a respective one of
said connecting portions and a forward end of at least one set of
said connecting portions in a direction in which said recording
paper is conveyed by said platen drum is positioned nearer to said
platen drum than a trailing end thereof in the direction in which
said recording paper is conveyed by said platen drum.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal printer and, in
particular, to a thermal printer in which recording paper is held
by and between a thermal print head including a plurality of
heating elements and a platen drum, the quantity of heat of the
heating elements is selectively changed while carrying the
recording paper, and an image is recorded on to the recording
paper.
2. Description of the Related Art
A thermal printer has been conventionally used as a printer of a
medical image diagnostic system in a medical treatment field. In
other words, in the medical treatment field, there are available
various kinds of medical image diagnostic appliances such as an
ultrasonic image projector, an X ray CT and the like which apply
ultrasonic waves, X rays or the like to a patient to detect the
change of the ultrasonic waves, X rays or the like to thereby
obtain an image of the affected part of the patient, and displays
the image, for example, on a CRT monitor as a visual image.
In the above-mentioned medical image diagnostic appliances, it is
convenient if the image of the affected part to be displayed on the
monitor can be provided in the form of a hard copy. For this
purpose, there have been developed various kinds of printers
including a thermal printer.
Also, besides the medical use, the thermal printer has been applied
to the surface printing of an ID card, a prepaid card and the
like.
As the thermal printer, there are known a heat transfer type
thermal printer and a heat sensitive thermal printer. Here,
referring to a thermal printer of a heat transfer type with
reference to FIG. 17, for example, recording paper 2 is fed one by
one from a paper feed cassette 1. A platen drum 6 clamps the
leading end of the recording paper by a clamper 7 and is then
rotated almost half way round to a printing part. In the printing
part, there are disposed a thermal print head 4 including a
plurality of heating elements 3 and an ink sheet cassette 5. The
thermal print head 4 and the platen drum 6 cooperate in holding the
ink sheet and the recording paper 2 fed between them. In this
holding condition, the heating elements 3 are driven in accordance
with an image signal supplied from a control device to thereby
transfer the image from the ink sheet to the recording paper 2. In
order to obtain a color image, areas Y, M and C are sequentially
formed in the ink sheet, and to which areas three kinds of ink,
that is, yellow (Y), magenta (M) and cyan (C) referred to as
subtractive primaries for printing are attached. The R, G and B
signals of a color image are respectively converted to YMC signals
and are then applied to the thermal head 4, so that the three-color
printing can be achieved.
After completion of the printing, the platen drum 6 is rotated
reversely and the printing paper is passed through a paper
discharge passage 8 and is inserted into a paper discharge tray 9
with the following end of the paper entering first.
In the above-mentioned conventional thermal printer, however, due
to the fact that the platen drum 6 is rotated almost half way
around and is positioned at the printing part after the the
recording paper 2 is clamped by the clamper 7, it takes a long time
from the paper feeding to the start of the printing.
Also, in the conventional thermal printer, after completion of the
printing, in order to prevent mutual interference between the
recording paper 2 and the ink sheet cassette 5, or to set the
following end of the recording paper at the entrance of the paper
discharge passage 8, the platen drum 6 is rotated at a given angle
in the same direction as in the printing time and is then rotated
reversely to thereby discharge the recording paper. This results in
a long printing time.
Further, according to the conventional thermal printer, an exit of
the paper discharge passage 8 is opened up in a paper guide wall
around the platen drum 6 and thus the paper guide wall is cut off
in this portion. For this reason, when the recording paper 2 is
clamped and rotated by the platen drum 6 and is passed through an
opening formed in a paper feed/discharge passage 8, the recording
paper 2 is caused to jump up at the edge of the opening due to its
rigidness or hardness, and this jumping problem adversely effects
the printing producing a slit mark.
Moreover, according to the conventional thermal printer, in order
to guide the recording paper 2 around the platen drum 6, several
auxiliary rollers are pressed against the platen drum 6 or a
wall-shaped paper guide member is used. However, the wall-shaped
paper guide member is divided into several portions because of the
necessity of the paper feed/discharge opening and due to the
forming limitations, and the connecting parts of the divided
portions are joined with one another in a smooth manner.
For this reason, the following end of the recording paper 2 is
caused to jump up at the stepped portions and clearances between
the connecting portions of the paper guide member to thereby
produce load variations. The load variations adversely effects the
printing.
In addition, in the conventional thermal printer, the thermal print
head 4 includes a plurality of heat sensitive elements arranged in
a direction perpendicular to the carrying direction of the
recording paper 2, and a voltage is applied based on an image
signal to thereby drive the heat sensitive elements so as to be
able to transfer a desired image from the ink sheet to the
recording paper 2. Such a thermal print head is mounted at the two
ends thereof to a arms. The thermal printer head 4 is disposed so
that it oscillates pair of oscillatory arms, with respect to the
platen 5 drum 6; and so that the thermal print head 4 may be
brought into contact with the platen drum 6 when printing. A spring
is mounted to each of the oscillatory arms and the springs press
the thermal print head 4 against the platen head when the thermal
print head 4 is in contact with the platen head.
However, in the conventional thermal printer, the pair of springs
may sometimes have different spring forces from each other.
Therefore, an even pressure cannot be applied to the platen drum 6,
and an uneven pressure during printing may be produced.
SUMMARY OF THE INVENTION
The present invention is directed towards eliminating the drawbacks
found in the above-mentioned conventional thermal printer.
Accordingly, it is an object of the invention to provide a thermal
printer which is capable of reducing a time to be taken from paper
feeding to print starting.
In order to achieve the above object, according to one embodiment
of the invention, there is provided a thermal printer comprising: a
recording paper storage part for storing a plurality of sheets of
recording paper respectively cut to a given length and piled on one
another; a recording paper feeding part for drawing out the
recording paper sheet by sheet; a platen drum for holding the
leading end of the recording paper drawn out by the recording paper
feeding part and winding the recording paper around the peripheral
surface thereof; a thermal print head for printing an image on to
the recording paper on the platen drum while rotating the platen
drum; and a recording paper discharge tray part, when the platen
drum is rotated again after completion of the printing, for
receiving the recorded paper carried by the rotating platen drum,
wherein a holding position on the platen drum holds to the
recording paper fed from the recording paper storage part and is
set just before a portion in which the thermal print head
prints.
According to the embodiment of the invention, the leading end of
the recording paper is held on the platen drum and, when the paper
holding position passes the thermal print head, printing is started
immediately, with the recording paper partially around. This can
reduce a time to be taken from paper feeding to print starting.
Also, it is another object of the invention to provide a thermal
printer which is capable of rotating a platen drum reversely to
discharge a sheet of recorded paper immediately after completion of
printing.
In order to attain this object, according to another embodiment of
the invention, there is provided a thermal printer which
comprising: a recording paper storage part for storing a plurality
of sheets of recording paper respectively cut to a given length and
piled on one another; a recording paper feeding part for drawing
out the recording paper sheet by sheet from the recording paper
storage part; a platen drum for holding the leading end of the
recording paper drawn out by the recording paper feeding part and
winding the recording paper around the peripheral surface thereof;
a thermal print head for printing an image onto the recording paper
on the platen drum while rotating the platen drum; and, a paper
discharge tray part for receiving, when the platen drum is rotated
reversely after completion of the printing, the recorded paper
carried by the reversely rotating platen drum with the following
end of the recorded paper entering first, rotary paper guide means
is provided which is used to guide the following end of the
recorded paper at the time of completion of the printing,
According to this embodiment of the invention, during the printing,
the rotary paper guide means is retreated from an ink sheet
cassette. Immediately when the printing is finished, the platen
drum is rotated in a reverse direction. In this operation, the
rotary paper guide means is rotated and part of the rotary paper
guide means is located at the position of the ink sheet cassette,
whereby the following end of the recorded paper is guided to a
paper discharge passage to prevent the recorded paper from
interfering with the ink sheet cassette. This prevents the platen
drum from rotating more than enough so that a printing time can be
reduced.
It is a further object of the invention to provide a thermal
printer which can prevent the recording paper from jumping up in an
opening formed in a paper feed/discharge passage, around a platen
drum.
In order to further embodiment accomplish this object, according to
the invention, there is provided a thermal printer comprising: a
recording paper storage part for storing a plurality of sheets of
paper respectively cut to a given length and piled on one another;
a recording paper feeding part for drawing out the recording paper
sheet by sheet from the recording paper storage part; a platen drum
for holding the leading end of the recording paper drawn out by the
recording paper feeding part and winding the recording paper around
the peripheral surface thereof; a thermal print head for printing
an image onto the recording paper on the platen drum while rotating
the platen drum; and a recording paper discharge tray part for
receiving when the platen drum is rotated again after completion of
the printing, the recorded paper carried by the rotating platen
drum, wherein an oscillatory piece member is provided in an opening
formed in the recording paper feed/discharge passage and faces
toward a paper guide around the platen drum in such manner that the
oscillatory piece member is free to oscillate and will never close
the opening, and also, when the recording paper is carried by the
platen drum, the oscillatory piece member closes the opening in the
paper feed/discharge passage and guides the recording paper.
According to this embodiment of the invention, the recording paper
is clamped on the platen drum and in this condition the paper is
guided by the paper guide, that is, the paper is rotated around the
platen drum. When the recording paper arrives at the opening in the
paper feed/discharge passage, then the recording paper pushes up
the oscillatory piece member so that the oscillatory piece member
closes the opening. The following end of the recording paper is
guided by this oscillatory piece member and is moved smoothly
through the opening in the paper feed/discharge passage.
It is a still further object of the invention to provide a thermal
printer which enables the following end of the recording paper to
be smoothly guided in the connecting portion of a paper guide
around the platen drum.
In order to another embodiment of achieve the above object,
according to theinvention, there is provided a thermal printer
comprising: a recording paper storage part for storing a plurality
of sheets of recording paper respectively cut to a given length and
piled on one another; a recording paper feeding part for drawing
the recording paper sheet by sheet from the recording paper storage
part; a platen drum for winding the recording paper drawn out by
the recording paper feeding part around the peripheral surface
thereof; a thermal print head for printing an image onto the
recording paper on the platen drum while rotating the platen drum;
and a paper discharge tray part for receiving, when the platen drum
is rotated again after completion of the printing, the recorded
paper carried by the platen drum, wherein a plurality of paper
guides are provided along the periphery of a platen at a given
distance from the platen drum, and also, in at least one set of the
connecting portions of the respective paper guides, the end thereof
on the leading side in the recording paper carrying direction is
positioned nearer to the platen drum than the end thereof on the
following side in the recording paper carrying direction,
According to the embodiment of the invention due to the fact that,
in the connecting portions of the paper guides, the end thereof on
the leading side in the carrying direction is positioned nearer to
the platen drum than the end thereof on the following side in the
carrying direction, there is eliminated the possibility that the
loads applied to the recording paper can be changed suddenly in the
connecting portions of the paper guides, for thereby preventing
deterioration of images printed.
It is a yet further object of the invention to provide a thermal
printer which can provide an even thermal print head pressure.
In attaining this object, according to this further embodiment of
the invention, there is provided a thermal printer comprising a
thermal print head for printing an image on recording paper on a
platen drum while rotating the platen drum, in which the two ends
of the thermal print head are pressurized and energized by springs
when they are abutted against the platen drum, and each of the
springs is supported by the two ends of a seesaw member which
oscillates about the central portion thereof, to thereby be able to
cancel a difference in force between the respective springs.
According to the invention, a pair of springs for energizing the
thermal print head are supported on the two sides of the seesaw
member. For this reason, even if the pair of spring have different
springs forces from each other, the spring forces can be made equal
to each other by inclining the seesaw member, so that the thermal
print head can be pressed against the platen drum with a uniform
pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
The exact nature of this invention, as well as other objects,
features and advantages thereof, will be readily apparent from
consideration of the following specification relating to the
accompanying drawings, in which like reference characters designate
the same or similar parts throughout the figures thereof and
wherein:
FIG. 1 is a view of the structure of a thermal printer according to
the invention, showing how paper is fed;
FIGS. 2 to an embodiment of 5 are respectively views of the
operation of a thermal printer according to the invention;
FIG. 2 is a view to embodiments of show how an image is initially
printed;
FIG. 3 is a view to show a state just before the recorded paper is
discharged;
FIG. 4 is a view to show the first half part of the paper discharge
process;
FIG. 5 is a view to show the second half part of the paper
discharge process;
FIG. 6 is a plan view of a recording paper feeding part employed in
an embodiment of the invention;
FIG. 7 is a perspective view of a clamper of a platen drum employed
in an embodiment of the invention;
FIG. 8 is an explanatory view of an intersecting portion between, a
fixed paper guide and a rotary paper guide around a platen;
FIGS. 9 (A) and (B) are respectively section views of a paper feed
passage and a paper discharge passage around a platen;
FIG. 10 is a perspective view of a structure for mounting a thermal
print head;
FIG. 11 is a plan view of a structure for mounting a thermal print
head;
FIG. 12 is a front view of the thermal print head mounting
structure shown in FIG. 11;
FIGS. 13 and 14 are respectively explanatory views of a structure
for preventing an ink sheet cassette from rotating in a reverse
direction;
FIG. 15 is an explanatory view of a structure for preventing an ink
sheet cassette from rotating in a reverse direction;
FIG. 16 is a section view of a structure of a take-up reel of an
ink sheet cassette; and
FIG. 17 is an explanatory view of a conventional thermal
printer.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Detailed descriptions will hereunder be given of the the preferred
embodiments of a thermal printer according to the present invention
with reference to the accompanying drawings.
Referring now to FIG. 1, there is shown a view of the structure of
a thermal printer according to an embodiment of the invention. The
thermal printer 10 of the invention consists mainly of a recording
paper storage part 12, a recording paper feed part 14, a platen
drum 16, an ink sheet cassette 18, a thermal print head 20, and a
paper discharge tray part 22.
Describing first the recording paper storage part 12, there is
disposed a paper feed tray 24 within the recording paper storage
part 12 and there is supported a recording paper peel-off member 25
within the storage part 12 in such a manner that the recording
paper peel of member 25 is free to oscillate about a shaft 26.
Within the paper feed tray 24, there are stored a plurality of
sheets of cut paper 28 in such a manner that they are piled on one
another. A receiving member 30 is disposed above the paper 28.
Also, the cut paper feed tray 24 includes a feed-out opening 32 in
the lower portion thereof.
Next, the recording paper feed part 14 includes gears 34, 36, 38
and 40 which intermesh with one another to thereby form a gear
transmission mechanism. A paper feed roller 42 consisting of a
rubber roller is disposed coaxially with the last gear 40. As shown
in detail in a plan view in FIG. 6, these gears 34 to 40 are
respectively supported by an oscillating arm unit means 44 which of
a pair of arms. The oscillating arm unit is supported by a shaft 46
and holds the paper feed roller 42 from both sides thereof. A gear
41, which is constructed as a free gear, is movable in an axial
direction with respect to a shaft 37 and is also pressed against
the gear 40 coaxial therewith by a spring 39. The gears 40 and 41
are given a rotational force by friction and, if a braking force of
a given force or greater is applied thereto, then the two gears are
idly rotated to function as torque, limiters, for thereby
preventing the gears from engaging with other too tightly. The
oscillating arm unit 44 can be oscillated about a shaft 46 and,
with the oscillation of the oscillating arm unit 44, the paper feed
roller 42 is allowed in a paper feed mode to be situated in the
feed-out opening 32 of the paper feed tray 24 to feed out the
recording paper 28 sheet by sheet. As will be discussed later, in
other modes than the paper feed mode, the paper feed roller 42 is
moved away from the paper feed tray 24 and is thus prevented from
feeding out the recording paper 28 carelessly when an image is to
be printed.
In other words, as shown in FIG. 6, stationary arc gears 79, 79,
which are respectively meshable with the gear 41 coaxial with the
gear 40, are allowed in other modes than the paper feed mode to
mesh with the gear 41 to thereby prevent the oscillating arm unit
44 from oscillating. The recording paper 28, which is fed out by
the paper feed roller 42, is guided by a fixed paper guide 48 and
is then sent to the platen drum 16 which will be described
below.
The platen drum 16 is constructed in such a manner that it can be
rotated about a shaft 50. The platen drum 16 includes a clamper 52
on the peripheral surface thereof. As shown in part in FIG. 7, the
clamper 52 includes a side plate 53 and the side plate 53 is
constructed such that it can be guided by means of elongated holes
54, 56, 56 and thus can be moved in the diametrical direction of
the platen drum 16. That is, the shaft 50 is fitted into the
elongated hole 54 and pins 58 (only one pin is shown in FIG. 7) are
respectively fitted into the elongated holes 56 (only one hole is
shown in FIG. 7), whereby the clamper 52 can be moved in the
diametrical direction of the platen drum 16. As shown in detail in
FIG. 7, the clamper 52 receives the leading end of the recording
paper 28 by a stopper 52A and moves down in the diametrical
direction of the platen drum 16 to thereby be able to clamp the
leading end of the recording paper 28. However, the clamping device
is not limited to the clamper shown in FIG. 7, but a pressure
roller or an air suction member can also be used. The platen drum
16 includes in the lower half periphery thereof a fixed paper guide
59 constructed in the form of a semi-circular shape. The paper
guide 59 is used to guide the recording paper 28 to the peripheral
surface of the platen drum 16.
Above the platen drum 16, there is disposed the ink sheet cassette
18 in an inclined manner. The ink sheet cassette 18 includes a
take-up shaft 60 and a supply shaft 62. In one printing, three
regions Y, M, C to which three different kinds of ink, that is,
yellow (Y), magenta (M), cyan (C), namely, three primary
colors.
In particular, at first, responsive to a yellow signal (Y) input to
the thermal print head 20, transfer by the yellow region the ink
sheet is executed by rotation of the platen drum 16.
Next, by rotation of the platen drum 16, the recording paper 28 is
set in such a manner that the ink can be superimposed and
transferred again onto the portion in which the yellow image has
been formed.
After then, an image signal corresponding to the magenta (M)
component is sent to the thermal print head 20. At this time, the
ink sheet is moved in such a manner that the next magenta region M
comes into contact with the recording paper 28 and, therefore, a
magenta image is superimposed and formed by the magenta ink onto
the yellow image.
Further, in a similar way, the recording paper 28 is rotated so
that the ink can be superimposed and transferred onto the portion
in which the images have been formed with the yellow and magenta
ink. In this turn, a signal corresponding to a cyan (C) image is
input to the thermal print head 20 and the ink sheet is moved such
that the next cyan region C comes into contact with the recording
paper 28, with the result that an image corresponding to the cyan
signal can be formed and superimposed with the cyan ink.
In this way, the yellow, magenta and cyan image signals are input
to the thermal print head 20, and the Yellow Y, magenta M and cyan
C inks of the ink sheet are superimposed on the same portion of the
recording paper 28 to thereby provide a color image.
Now, above the ink sheet cassette 18, there is disposed the thermal
print head 20 in such a manner that it is free to oscillate about a
shaft 64. The thermal head 20 includes a plurality of heat
sensitive elements 66 respectively arranged in a direction
perpendicular to the conveying direction of the recording paper 28.
The thermal print head 20 applies a voltage to the heat sensitive
elements 66 in accordance with the image signals to drive the heat
sensitive elements 66 to thereby transfer a desired image from the
ink sheet to the recording paper 28.
The printing position of the thermal print head 20 is set just
behind the clamping position of the clamper 52. After printing if
the platen drum 16 is rotated reversely, then the printed paper 28
is delivered to the paper discharge tray part 22 through a paper
discharge passage 72 which is formed by fixed paper guides 68 and
70. In other words, after the printed or recorded paper 28 is sent
to the paper discharge passage 72 by the reversed rotation of the
platen drum 16, if the trailing end of the paper 28 is held by
paper discharge rollers 74, 76, then the leading end of the
recorded paper 28 is released from the clamper 52, whereby the
recorded paper 28 can be fed by the paper discharge rollers 74, 76
and can be stored within the paper discharge tray part 22.
Next, a description will be given below of a movable paper guide
mechanism. A drive lever 80 is constructed such that it can be
freely oscillated about a shaft 82, and the drive lever 80 includes
a flat portion 84 in the right end portion thereof and a forked
portion 86 in the left end portion thereof. The drive lever 80 is
rotationally energized counter clockwise about the shaft 82 by a
spring 88. On the other hand, a movable lever 90 is constructed
such that it can be freely oscillated about a shaft 92, and the
movable lever 90 includes a movable paper guide 91 in the upper end
portion thereof and a pin 93 in the lower end portion thereof, with
the pin 93 being in engagement with a U-shaped groove formed in the
forked portion 86. The movable lever 90 is rotationally energized
clockwise about the shaft 92 by the spring 88. When a projection
portion 45 provided in the oscillating arm unit 44 is not in
contact with the flat portion 84 of the drive lever 80, then the
leading end 91A of the movable guide 91 is inserted into the ink
sheet cassette 18 (see FIG. 1 and FIG. 4).
Next, a description will be given below of a rotary paper guide
mechanism. A rotary paper guide 94 is supported through a pair of
arms 96 by a shaft 50 of the platen drum 16 in such a manner that
the rotating paper guide 94 can be rotated about the shaft 50. The
rotary paper guide 94 is formed as an arc shape extending along the
outer periphery of the platen drum 16 and includes an end portion
94A which is located near to the fixed paper guide 59 in such a
manner that the end portion 94A and the end portion 59A of the
fixed paper guide 59 can intersect each other. As shown in FIG. 8,
the rotary paper guide 94 can be rotated only by a distance
designated by l. Also, the rotary paper guide 94 can be rotated
about the platen drum 16 by a drive mechanism (not shown) according
to the paper feed states, printing states and paper discharge
states (see FIGS. 1 to 5).
Referring now to FIGS. 9 (A) and (B), there is shown a structure in
the neighborhood of the paper feed and discharge passages located
round the platen drum 16. There is provided a paper feed passage 49
which is interposed between the paper guide 48 and paper the guide
70. Also, a paper discharge passage 72 is also interposed between
the paper guide 70 and the movable paper guide 91. The paper feed
passage 49 includes an opening in which an oscillatory piece member
98 is supported through a shaft 100. Also, the paper discharge
passage 72 includes an opening in which another oscillatory piece
member 102 is supported through a shaft 104. The two oscillatory
piece members 98, 102 are supported or journaled in a free state
and can be easily oscillated by the leading or trailing end of the
recording paper 28.
Preferably, the sliding contact surface of the oscillatory piece
member 98 may have such a shape that can match the curved surfaces
of the other paper guides 59, 91.
In the above-mentioned embodiment, the oscillatory piece members
are provided on both of the paper feed and discharge passages 49,
72. Alternatively, however, they may be provided in one of the feed
or discharge passages 49, 72.
The detailed structure of the fixed paper guide 59 is shown in
FIGS. 9 (A), (B). In a connecting portion between the paper guides
59 and 48, the end portion 48A of the paper guide 48 located
forwardly in the recording paper conveying direction comes nearer
to the platen drum than the end portion 59A of the paper guide 59
located rearwardly in the recording paper conveying direction. For
this reason, in the neighborhood of the connecting portion between
the paper guides 48 and 59, as shown in FIG. 9 (A), the trailing
end of the recording paper 28 is guided by the end portion 48A of
the paper guide 48, and is free from the influences of the
connecting portion between the paper guides 59 and 48, so that the
trailing end of the recording paper 28 can be moved apart from the
paper guide 59 smoothly.
As shown in FIG. 10, the thermal print head 20 is mounted through
L-shaped brackets 95 to the tip ends of oscillatory arms 97A, 97B.
The L-shaped brackets 95 include pins 106, 108 which are
respectively projecting towards the oscillatory arms 97A, 97B from
the brackets. The pin 106 is loosely fitted into a transversely
elongated hole 110 formed in the oscillatory arms 97A, 97B, while
the pin 108 is loosely fitted into a longitudinally elongated hole
112. For these reasons, the mounting portion of the thermal print
head 20 has a freedom of movement so that the thermal can follow
the inclining movement of the platen drum 16.
As shown in FIGS. 10 to 12, the base end portions of the
oscillatory arms 97A, 97B are respectively supported through shafts
64A, 64B by a base plate 113. In other words, the base end portion
of the oscillatory arm 97A is journaled through an E ring 114 on
the shaft 64A and the oscillatory arm 97B is energized in the right
direction in the figures by a spring 116. Therefore, the
oscillatory arms 64A, 64B, to which the thermal print head 20 is
connected, are energized in the right direction and the E ring 114
serves as a reference surface. This prevents the thermal print head
20 from shifting out of position.
As shown in FIG. 10, a seesaw lever 118 is supported by the side
plate 120 in such a manner that the seesaw lever 118 can freely
oscillate. In other words, a pin 122 provided projectingly on and
from the central part of the seesaw lever 118 is loosely fitted
into a circular hole 124 formed in the side plate 120, so that the
seesaw lever 118 is free to oscillate about the central portion
thereof. The lower ends of springs 126 are respectively mounted to
the two ends of the seesaw lever 118, while the upper ends of the
springs 126 are respectively mounted to the tip ends of levers 128.
The levers 128 are respectively journaled through shafts 130 onto
the base plate 113 and the base end portions of the levers 128 are
respectively journaled through pins 132 on the first ends of levers
136. Also, normally, the lever 128 are abutted against a stopper
150 projecting from the base plate 113 to charge a spring force.
The second ends of the levers 136 are respectively connected
through common shafts 138 to the first ends of levers 140. The
levers 140 are respectively journaled on the oscillatory arms 97A,
97B. Also, levers 141 are respectively journaled on the common
shaft 138 and the second ends of the levers 141 are respectively
journaled through pins 144 on the first ends of drive levers 142.
The second ends of the drive levers 142, 142 are respectively fixed
to a drive shaft 146.
The drive shaft 146 is connected to a motor (which is not shown)
and, if the drive shaft 146 is rotated clockwise in FIG. 10, then
the drive lever 142 is rotated clockwise to rotate the oscillatory
arms 97A, 97B counter-clockwise through the levers 141, 140. As a
result of this, the thermal print head 20 is brought into contact
with the platen drum 16 and further, when the levers 128 are moved
apart from the stopper 150, then the springs 126 pushes and
energizes the thermal print head 20 through the levers 128, 136,
140. At this time, if the spring forces vary between the springs
126, then the seesaw lever 18 is inclined to pull the weaker spring
more greatly than the stronger spring to thereby equalize the
springs respectively applied to the levers 128. As a result of
this, the thermal print head 20 can be energized toward the platen
drum 16 with a uniform force.
On the other hand, if the drive shaft 146 is rotated
counter-clockwise, then the drive lever 142 is rotated
counter-clockwise and the levers 128 are abutted against the
stopper 150. Thereafter, the thermal print head 20 is rotated
clockwise and is thus moved apart from the platen drum 16.
A description will be given below of the operation of the
embodiment of a thermal printer constructed in the above-mentioned
manner according to the invention.
At first, as shown in FIG. 1, the oscillatory arm unit 44 is
rotated clockwise to push the recording paper peel-off member 25
and the piled-up sheets of recording paper 28 upwardly. The upper
portion of the recording paper 28 is brought into contact with the
receiving member 30 and, in this state, if the paper feed roller 42
is rotated counter-clockwise, the recording paper 28 is sent out
sheet by sheet from the feed-out opening 32 by the paper feed
roller 42. Then, the recording paper 28 is guided along the fixed
paper guide 48 and is abutted against the stopper 52A of the
clamper 52 of the platen drum 16 shown in FIG. 7. If the recording
paper 28 is abutted against the stopper 52A of the clamper 52, then
the clamper 52 is moved down in the diametrical direction to clamp
the leading end of the recording paper 28. In this state, the
platen drum 16 is rotated counter-clockwise and thereafter the
thermal print head 20, as shown in FIG. 2, is oscillated counter
clockwise and printing is started just after the recording paper 28
is clamped. At this time, the oscillatory arm unit 44 is oscillated
counter-clockwise about the shaft 46, while the projection portion
45 of the oscillatory arm unit 44 is pressed against the flat
portion 84 of the drive lever 80. If the projection portion 45 of
the oscillatory arm unit 44 is pressed against the flat portion 84,
then, as shown in FIG. 2, the drive lever 80 is rotated clockwise
against the energizing force of the spring 88 and further the
movable lever 90 is rotated counter-clockwise about the shaft 92 to
thereby retreat the leading end 91A of the movable paper guide 91
from the ink sheet cassette 18
At the same time, the rotary paper guide 94 is rotated
counter-clockwise to a position in which the lower end portion 94A
thereof intersects the fixed paper guide 59 deeply. In this
position, as shown in FIG. 2, the upper end portion 94B of the
rotary paper guide 94 is retreated from the ink sheet cassette
18.
The image printing is started in the state shown in FIG. 2 and the
platen drum 16 is rotated counter-clockwise.
In a thermal printer according to the present embodiment, due to
the fact that the clamping position of the leading end of the
recording paper the platen drum is set at a position just before
the printing part and the image printing is started immediately
after the leading end clamping position passes through the thermal
print head 20, a time necessary from the feeding of the recording
paper 28 to the printing start time can be shortened.
In the image printing on the platen drum 16, the printing
conditions of Y, M, C are different from one another. In other
words, for the Y printing, as shown in FIG. 2, the image is printed
on the recording paper 28 in a state in which the recording paper
28 is not wound around the platen drum 16 and, for the M, C
printing, as shown in FIG. 3, the image is printed on the recording
paper 28 in a state in which the recording paper 28 is wound round
the platen drum 16. For this reason, in order to establish the
uniform printing condition, a pressure roller may be disposed in
the paper feed passage in the Y printing to thereby apply loads
such as a friction force or the like to the recording paper 28.
In the state shown in FIG. 2, if the platen drum 16 is rotated and
the recording paper 28 is positioned in the openings in the paper
feed passage 49 and paper discharge tray passage 72, then, as shown
in FIG. 9 (A), the oscillatory piece members 98, 102 are pushed up
and further, if the trailing end of the recording paper 28 is
situated in the opening, then the oscillatory piece members 98, 102
close the opening, for thereby preventing the trailing end of the
recording paper 28 from jumping up at the edge of the opening.
In the state shown in FIG. 2, if the platen drum 16 is rotated
counter-clockwise, then the recording paper 28 is guided
counter-clockwise as shown in FIG. 9 (A). When the trailing end of
the recording paper 28 is going to pass through the connecting
portion between the paper guide 48 and paper guide 59, as shown in
FIG. 9 (A), the trailing end of the recording paper 28 is guided by
the end portion 48A of the paper guide 48 and is thus moved apart
from the end portion of the paper guide 59, for thereby preventing
the trailing end of the recording paper 28 from jumping up in the
connecting portion.
In the above embodiment, the present invention is applied to the
connecting portion between the end portion 48A of the fixed paper
guide 48 and the fixed paper guide 59. Alternatively, however, the
present invention can also be applied to the connecting portion
between the fixed paper guide 59 and the rotary paper guide 94.
As shown in FIG. 3, when the printing is completed and just before
the paper is discharged, the thermal print head 20 is oscillated
clockwise to retreat from the printing position and the oscillatory
arm unit 44 is rotated clockwise about the shaft 46, whereby the
drive lever 80 is rotated counter-clockwise by the energization
force of the spring 88 to rotate the movable lever 90 clockwise
about the shaft 92, for thereby inserting the leading end portion
91A of the movable paper guide 91 into the ink sheet cassette 18.
At the same time, the rotary paper guide 94 is rotated clockwise
and the upper end 94B of the rotary paper guide 94 is situated
within the ink sheet cassette 18. In this state, the platen drum 16
is rotated reversely and the trailing end of the recording paper 28
is guided by the rotary paper guide 94 and movable paper guide 90
into the paper discharge passage 72, without being inserted into
the ink sheet cassette 18 or into a recessed portion 20A in the
thermal print head 20. The recording paper 28 guided to the paper
discharge passage 72 is further guided to the paper discharge
rollers 74, 76, when the clamping of the recording paper 28 by the
clamper 52 is released. After then, the recording paper 28 is
driven by the paper discharge rollers 74, 76 and is then stored
into the paper discharge tray 22.
In the above-mentioned embodiment, the rotary paper guide mechanism
and the movable paper guide mechanism are used in combination.
Alternatively, however, if the amount of rotation of the rotary
paper guide mechanism is increased, then it is possible to achieve
a desired effect only by using the rotary paper guide
mechanism.
As has been described heretofore, according to the thermal printer
of the present invention, due to the fact that immediately after
completion of the printing, the platen drum 16 can be rotated
reversely to discharge the printed paper, it is possible to prevent
the platen drum 16 from rotating wastefully and the printing time
can be reduced.
Referring now to FIG. 13, there is shown a detector which is used
to detect the recording paper. In particular, the light from a
light emitting part 200 disposed above the platen drum 16 is turned
about 90.degree. by a mirror (or a prism) 202 provided in the
platen drum 16 and then reaches a light receiving part 204 provided
on the side portion of the platen drum 16. When the recording paper
28 is not fed, the detector is situated at a position to be able to
detect the HP (home position) of the platen drum 16. When the
recording paper 28 is fed and reaches the stopper 52A of the
clamper 52, then the light receiving part 204 is shielded by the
recording paper 28 from the light from the light emitting part 200,
for thereby detecting the completion of the paper feeding.
In this manner, the HP as well as the paper feed completion can be
detected by only one sensor, which results in the improved position
accuracy.
Referring now to FIG. 14, the light from the light emitting part
200 is applied to two mirrors 208, 210 by use of a partition plate
206 and these lights are then reflected onto a platen drum HP
detect sensor 212 and a recording paper sensor 214. The platen drum
HP detect and recording paper sensors 212 and 214 are disposed in
such a manner that in the recording paper feed completion position
the sensor 214 is shielded from the light while the sensor 212 is
not shielded. Due to this, the following four positions can be
detected:
______________________________________ Sensor 212 O O X X Sensor
214 O X O X State Platen Paper Platen rotates Recording HP Feed
forwardly paper Position Completion and approaches is being its HP
position conveyed ______________________________________ O Light is
received. X Light is shielded.
Referring now to FIGS. 15 and 16, there are shown the internal
structures of the ink sheet cassette 18 and a take-up reel. A
take-up hub 300 includes an end portion 314 engageable with a
take-up shaft 60 around which an ink sheet 302 is to be wound. The
take-up hub 300 is connected to a ratchet wheel 312 by a shaft 316.
In the ratchet wheel 312 there is disposed a ratchet 320 in such a
manner that the ratchet 320 is engageable with the ratchet wheel
312. The ratchet 320 does not engage with the ratchet wheel 312
when the take-up hub 300 is rotating in the winding direction, but
the take-up hub 300 engages with the ratchet wheel 312 in the
reversed rotation of the take-up hub 300 to thereby prevent the
take-up hub 300 from rotating in the reverse direction On the other
hand, on the contact surface of the take-up hub 300 and the contact
surface between the take-up hub 300 and an inner cylinder 306,
there are disposed felts 318, 308, respectively, and the inner
cylinder 306 is energized by a spring 310 to press against the
take-up hub 300. Also, the take-up hub 300 includes a take-up gear
304 which is connected to a drive motor through a gear transmission
mechanism (not shown). If the take-up gear 304 is rotated in the
winding direction by the drive motor, then the take-up hub 300 is
rotated at a constant torque by the friction force of the felts
318, 308, so that the ink sheet 302 can be wound around the take-up
shaft 60.
The ink sheet 302 is drawn out from the supply shaft 62 in the
order of the Y, M, C regions. In this operation, even if the ink
sheet 302 and the recording paper 28 are thermally fused and
attached to each other to thereby produce a possibility of rotating
the take-up shaft 60 in the reversed direction due to conveying of
the recording paper 28, the ink sheet 302 can never be fed
reversely because the take-up shaft 60 is locked by the ratchet
320.
As has been described heretofore, in the thermal printer of the
present invention, even if the ink sheet and recording paper 28 are
attached to each other by thermal fusion 302, the reversal
preventive mechanism prevents the ink sheet 302 from being fed in
the reversed direction, so that it is possible to prevent jamming
or the like of the ink sheet.
Although the above-mentioned embodiment description has been given
for the thermal printer of a heat transfer type, the present
invention can also apply to a thermal printer of a heat sensitive
type.
According to the above-mentioned embodiment, there is used an
ordinary ink sheet for color printing in which three colors, that
is, yellow, magenta and cyan are formed sequentially in the
different regions thereof. According to the invention,
alternatively, an ink sheet for photo-engraving can also be used
which is formed by coating a single color of ink thereon. When
using such an ink sheet with a single color of ink, a superimposing
signal of YMC may be applied to the thermal print head to execute
printing once by use of the single color ink sheet.
It should be understood, however, that there is no intention to
limit the invention to the specific forms disclosed, but on the
contrary, the invention is to cover all modifications, alternate
constructions and equivalents falling within the spirit and scope
of the invention as expressed in the appended claims.
* * * * *